On the basis of some good detective work, it now seems clear that the original recording of the Ravel Piano Concerto does not, after all, feature the composer at the keyboard but rather Marguerite Long. There is no doubt, however, that Ravel supervised the recording session and was in attendance for the entire experience. Listening to this disc today, it is apparent that the jazzy nature of the piece was paramount in the composer’s ear.

This might seem obvious to a reader of the score, but over the years I have heard many live performances of the work and they have been almost universally deficient, seemingly embarrassed to let their hair down and swing a little. It was therefore surprising to encounter a fine execution of the piece at, of all places, the Mostly Mozart Festival.

Jean-Yves Thibaudet’s avocation as a jazz pianist allowed him to immerse us all in the idiom courageously, with no false sense of decorum. Maestro Louis Langree must have really cracked the whip at rehearsals, for the orchestra was rhythmically correct throughout – correct meaning slightly off-center and verging on the syncopated in this case.

Mr. Thibaudet also impressed by playing softly. The Mostly Mozart gang is a relatively small orchestra, and this pianist adopted more of a jazz-combo rather than a big-band approach. His long runs and arpeggiated passages in the outer movements were the epitome of sophistication, cool rather than hot. Although I found his long introduction to the Adagio a little sing-song – nowhere near as poignant as, say, the old Leonard Bernstein recording conducted from the piano – his overall shaping of the movement was little short of gorgeous. The oboist played this incredible line’s reprise with heart-melting sincerity, although the horn absolutely tortured Ravel’s most precious phrases.

A lively and colorful “Mother Goose Suite,” notable for the clean interplay of instrumental lines and the precise definition of timbral effects, began the program. Especially impressive were the subtle shadings of the Tom Thumb section and the otherworldliness of the Fairy Garden.

There was also Mozart on the program. The “Paris” Symphony, No. 31, was performed crisply and with a great sense of musical excitement, reveling in the devices of crescendo, known in those days as the “Mannheim roller,” and accelerando. This orchestra is now at the top of its game, and sounds too good for a summer replacement. Perhaps the new, central positioning of the stage and its acoustical panels hanging from the ceiling helped a bit. In any case, this was a much clearer rendition of an 18th-century work than anyone would receive from the normal house band that monopolizes Avery Fisher through the main season.

In fact, this was close to the modern ideal of a Mozart symphonic performance. The orchestra is properly downsized so that each instrumental idea is clearly expressed with none of the muddiness of a 100-piece behemoth. The tempi were lively throughout, the touch of the conductor light and nimble, the totality of the aural impression decidedly pleasant. For a 21st-century listener, this type of rugged yet gentle approach is a satisfying compromise of Deist ideas expressed in post-mechanized Western style.

Sir James Galway was on hand for a turn at Mozart as well. Despite his popularity, Mr. Galway is a fine musician who has been performing Wolfgang for many years, even performing with Paddy Moloney and the Chieftains in their own composition, “Planxty Mozart” (roughly “in the style of Mozart” in Gaelic), a rollicking, popularly styled adaptation of the elan vital of this endlessly fascinating and enduring boy genius.

About halfway through the seemingly endless Concerto for Flute and Harp, K.299, however, I wished for the Moloney version so that some life might be infused into the proceedings. This particular piece is one of those deadly, plodding Mozart efforts, long on harmonic resolution but short on melodic invention. Even the clean technique of Welsh harpist Catrin Finch – she is Prince Charles’s personal harpist (it’s good to be a royal) – did not divert for long.

The net result was simple tedium, although performed about as well as such soporific noodling can be. “Die Zauberflote” notwithstanding, Mozart professed a hatred for the flute, and this effort may be the most convincing argument for his personal distaste. The audience would have been much better served with a more generous helping of Irish and Welsh melodies that Mr. Galway and Ms. Finch served up as an encore. And speaking of that audience, after the final symphony, with typical New York rudeness, they ran out of the hall as if the building were on fire.